MetalCenter-Dependent Selectivity Divergence in MN₄ Single-Atom Catalysts for Aerobic HMF Oxidation

Area of Science:

• Catalysis
• Sustainable Chemistry
• Materials Science

Background:

• Selective oxidation of 5-hydroxymethylfurfural (HMF) is crucial for sustainable chemical production.
• Controlling selectivity in HMF oxidation is challenging due to similar energy gaps between reaction intermediates.

Purpose of the Study:

• To synthesize and investigate two single-atom catalysts (SACs) with M-N4 configurations for HMF oxidation.
• To understand the role of the metal active center in determining product selectivity and reaction mechanisms.

Main Methods:

• Synthesis of FeN4 and CoN4 single-atom catalysts.
• Characterization of catalytic performance for HMF oxidation.
• Density Functional Theory (DFT) calculations to elucidate reaction mechanisms and intermediate adsorption.

Main Results:

• FeN4 catalyst achieved 99.9% HMF conversion and 93.9% selectivity to 2-formyl-5-furancarboxylic acid (FFCA).
• CoN4 catalyst predominantly produced 2,5-furandicarboxylic acid (FDCA) with comparable HMF conversion.
• DFT revealed that the metal center dictates FFCA intermediate adsorption and O2 activation pathways, leading to distinct product outcomes.

Conclusions:

• The metal active center in M-N4 SACs effectively controls the selectivity of HMF oxidation.
• FeN4 and CoN4 catalysts exhibit different mechanisms for O2 activation and intermediate handling, guiding product formation.
• This work provides a mechanistic basis for designing catalysts to tailor selectivity in HMF oxidation via electronic structure manipulation.